Myo-Inositol appears to be universally distributed in nature and scyllo-inositol is found to accompany myo- whenever sufficiently sensitive methods have been used. While myo-inositol has a clearly defined function as precursor of the phosphoinositides it is widely held that it has other important functions also. Scyllo-Inositol has no known function. These two inositols are found in high concentration in nervous tissue. The objectives of the proposed research are to determine whether scyllo-inositol is managed by the animal in a way that indicates it is a necessary component in the animal's economy. I feel that this must be established because of the possibility that scyllo- may be an evolutionary artifact. Simultaneously with these studies I will examine myo-inositol in a way that could inform us about its secondary functions. I believe both these ends can be met by an approach which develops an understanding of 1) the means by which brain and kidney transport or retain inositols by selective processes, 2) the distribution and concentrations of the inositols at the cellular level, especially in brain and nerve and, where possible, in different functional states in these tissues and, 3) the specific, selective and controlled enzyme pathways which synthesize the inositols. These ends will be met by 1) studying the uptake of inositols across the blood- brain barrier in the intact rat and the uptake and efflux of inositols from brain and kidney slices, 2) measuring the levels and distribution of inositols in 1-10 nanogram dry weight tissue samples and single cells as well as looking for variations in levels in hypothalamus during endocrine states of the rat and 3) studying the nature of the enzyme in mammals, especially in brain, which interconvert the inositols and reduce inososes and the enzyme that carries out the biosynthesis of myo- inositol as well as the distribution of these enzymes.